This invention relates to a safety ski binding comprising a sole plate which is releasably connected to the ski by a trunnion located approximately beneath the heel and further comprising a sole mount affixed to said sole plate and a heel assembly which is adapted to pivot about an axis perpendicular to the ski under spring tension and which co-operates via a cam with a curved member which is rigidly attached to the ski, which centers said heel assembly in a middle position and along which the cam glides when said sole plate is twisted, thereby tensioning the spring and pivoting said heel assembly to release the boot.